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Topic Review (Newest First)

01-05-2015 05:32 PM

AquaDwell

EDIT: After reading the LED FAQ, my questions have been answered.

03-24-2013 01:03 AM

Hoppy

You really have to use a PAR meter to find out how much light you get for that fixture. I notice it can be dimmed, and I suspect you will have to dim it to avoid having too much light for a planted tank.

I'm getting very close to a good design for a conversion of a cheap lux meter to a waterproof PAR meter, so if you want to be on the list for possibly buying one, PM me and I will add your name to my list. It would be way cheaper than buying a commercial PAR meter.

03-23-2013 07:57 AM

Kanne26

Wow this whole thread is intense and way over my head (I started on the PAR vs Distance thread to attempt to learn how much PAR my LED strip is giving out).... I still have no idea. Can someone help me? I currently have a 20gal high with one of these sitting on top of it: http://www.aquariumplants.com/LumenB...m?1=1&CartID=0. I keep hearing that LEDs aren't strong enough to grow plants, but others have told me this is super high lighting... so I'm gettin' a bit confused! I don't wanna over or undercook my plants. I'd like my PAR to be around 30-40.....

05-14-2012 11:42 AM

justdaman

hey guys! just want to know if this kind of led fixture can properly light up a 2ft tall tank. i was thinking of putting 8 of these along a 6x2x2ft tank

A 20 gallon high tank is roughly 24L x 12D x 16H. I don't think a 10" x 10" heatsink would be good for that. Much better would be a 18-20" long heatsink which could be as narrow as 2-3 inches. A piece of extruded aluminum channel would work fine, since you intend to use it at low current.

Using 6 Cree XM-L evenly spaced along that heatsink, say 3 inches apart, running at 400 mAmps should give you about 40 micromols of PAR at the substrate, with the light sitting on top of the tank, with no optics. Raise it about 6 inches and you should get about 30 micromols of PAR, good low light. If you zig-zag the LEDs across the top of the tank so you effectively have two rows, with them spaced about 3.5 inches apart on diagonals - two rows 1.5 inches apart - you should get about 3/4 of that PAR, so you could sit the light right on top of the tank for low light. Then the plants wouldn't grow to the middle quite as much, and the PAR from front to back of the substrate would be more uniform.

02-04-2012 07:02 PM

Chlorophile

How many / what kind of LED's would be good for a low light 20G High.

I like the idea of having some of that nice ripple effect, but at the same time I don't want stems all growing towards the middle or something.

Would 6 XM-L's on a 10"x10" heatsink work? I'd probably under drive them around 400mA.
Seems like it might be too bright.
It'd have to be passively cooled too I can't stomach the idea of a fan.

12-01-2011 04:15 AM

tentacles

Not related to the previous post, but I just had a look at the Cree XPG lifespan documents (they have so far actually completed over 10000 hours of actual testing), and the XPG series holds up quite a lot better than previous ones.. At 55C case and 55C ambient (ambient is actually very important to lifespan), at 1A current at 6000h the LED still produced 100% of output. The L70 life (down to 70% brightness) at 85C/85C/1A is estimated at over 60000 hours.

I don't know about you guys, but I expect that I'll replace my emitters in under 5 years - think about it, in 5 years there will be some REALLY amazing stuff on the market, probably with spectra specifically designed to make plants grow like algae and the colors of our fish melt our eyes.

I'm looking at building a couple lights that will have 4 different channels of LEDs independently controlled. Each channel would have 4-12 LEDs. I would be using an Arduino board to control these channels via PWM. Any red flags in this spec sheet that I'm overlooking?

Quick question for you folks running LEDs.. How much far do LEDs with optics stick out from the surface they're mounted to? I'm trying to figure out how much clearance I need for the enclosure.

11-28-2011 10:42 PM

silvawispa

I have no direct experience with the 660nm lights, but maybe I can point you at some info.

I've been reading some studies on the effects of light frequencies on aquatic plant growth and come across some interesting results.
Sadly I haven't saved my sources, but google is your friend too!

All studies I looked at were done with freshwater aquatic plants typically found in an aquarium. I think that is quite important!

One study I looked at concluded that red light was implicated in creating compact branched growth, green light(as might be found in a deeper lake) gave leggy growth(long internodes, lower chlorophyll) with white light and blue light giving a more 'normal' growth.

The upshot for me, is that my next LED purchase will be a combination of warm white, that has a good dollop of the 600-700nm wavelengths, whilst not being exactly short of blue light either, and the midrange white LEDs so I don't end up with a 'yellow' tank. These should compliment my cold 'daylight' whites and provide well for the plants.
Time will tell.

If I had gone the 'many small sources' route, I would consider mixing in some reds to encourage the compact growth, but I've seen some messy shadows from that sort of set-up so I'd be thinking hard about the design. I didn't, I've gone for few lights, but powerful.
My feeling is that the white LEDs now available have a suitable enough spectrum coverage for a good looking, strongly lit, healthily growing planted aquarium.

The main focus of my reading was how plants adapt to different wavelengths as they become available, for example as water depth changes or the plant grows.
It seems that some plants do adapt to different light frequencies and some don't...

10-24-2011 02:17 AM

Naekuh

can someone tell me about how 660nm led's work in fresh water fish tanks?

Are they good but make things look funny? or they asking for an algae bloom on biblical levels?

Wondering if 660nm LED's should be considered as cree makes them in 3W sizes too.

05-19-2011 09:54 PM

cggorman

I know that Cree XR and XP series diodes are far and away the most popular emitters in the hobby, but I feel they have less than ideal spectral distribution. For my project, I decided to use LedEngin LZ1 neutral white for my main source. Unfortunately, even those have a big shortfall in CRI compared to the flourescent sources I am replacing. To supplement the white LEDs and hopefully correct the CRI up to something more acceptable, I added Lexeon Rebel 505nm (cyan). A careful comparison to natural daylight also shows a slight defficiency in the far red end of the spectrum so I also added LedEngin reds in both 660nm and 735nm. The 735 is sketchy, but I wanted to try it. The 660s are at a photosynthetic response spike and also help show off the red in my fish.

You may wonder about the ultraviolet end of the spectrum...After testing with three or four different colors from 400nm down to about 320nm, I found the fish turned black (no flourescence), floating particulates in the water flouresced unaesthetically (turning the water milky in appearance), and read several articles indicating that UV was at best marginally beneficial (if not detrimental) to the health of both the fish and the plants...so I elected to leave that piece of the spectrum out. (not to mention the emitters are expensive)

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